Dr. Anthony Fauci co-authored a research paper concluding that face masks were responsible for the majority of deaths during the 1918 Spanish flu pandemic.
Social media platforms have repeatedly circulated a rumor alleging that Dr. Anthony Fauci—the former director of the National Institute of Allergy and Infectious Diseases—published scientific findings stating that face coverings caused most fatalities during the early-20th-century Spanish flu outbreak.
For instance, posts shared across platforms like Facebook have claimed that a 2008 paper co-authored by Fauci revealed that Spanish flu victims primarily succumbed to “bacterial pneumonia caused by wearing masks.” These posts frequently questioned why a public health official who understood this dynamic would later support mask mandates.
(Example of social media claims)
While Fauci did indeed co-author a study investigating bacterial pneumonia deaths during the 1918 pandemic, that research made no mention of face masks whatsoever. Furthermore, when questioned by the Associated Press, Fauci explicitly dismissed the notion that masks played any role in those bacterial infections. Consequently, the claim has been rated false.
What Did the 2008 Study Actually Conclude?
The research paper in question is real. Titled “Predominant Role of Bacterial Pneumonia as a Cause of Death in Pandemic Influenza: Implications for Pandemic Influenza Preparedness,” it was published on October 1, 2008, in The Journal of Infectious Diseases.
The research team analyzed lung tissue from 58 historical autopsies and reviewed data from 109 previously published reports covering 8,398 individual autopsies. They determined that the vast majority of fatalities during the 1918–1919 pandemic were the result of secondary bacterial pneumonia caused by microbes commonly found in the upper respiratory tract.
Crucially, the study did not attribute these infections to face masks. A search for terms like “masks” or “face coverings” within the document yields no results, and the authors drew no connection between protective gear and bacterial pneumonia.
An official news release issued at the time further clarified the mechanism: the influenza virus compromised the respiratory lining, creating a pathway for normal upper-respiratory bacteria to invade the lungs. Fauci famously described the dynamic by noting that the virus “landed the first blow while bacteria delivered the knockout punch.”
The paper’s authors emphasized that future pandemic planning should prioritize the availability of antibiotics and bacterial vaccines alongside antiviral drugs. Public health agencies like the U.S. Centers for Disease Control and Prevention have similarly pointed out that modern antibiotics—which were unavailable in 1918—are the key treatment for secondary bacterial infections associated with influenza.
Addressing the rumors directly in a 2003 interview with the Associated Press, Fauci reiterated that while some patients suffered from deadly secondary bacterial complications, the influenza virus itself remained the primary driver. He characterized claims linking these deaths to masks as unfounded “nonsense.”
Is There Any Evidence That Masks Cause Bacterial Pneumonia?
Medical experts have repeatedly debunked the idea that routine mask-wearing leads to respiratory infections. Infectious disease specialists and health institutions have confirmed there is no evidence connecting proper mask use to bacterial, fungal, or viral lung infections.
While scientific studies analyzing used masks have occasionally detected accumulated bacteria on the fabric, detecting microbes on a discarded mask does not prove that wearing it causes pneumonia. Research focusing on hospital workers, for instance, has found that N95 respirators actually protect against bacterial colonization rather than promote it.
While health guidelines naturally recommend keeping face coverings clean and replacing them when visibly soiled or damp, standard use does not cause bacterial pneumonia.
Examining the Numbers: Where Did the “90%” Claim Come From?
Viral social media posts often assert that “90% of the 50 million deaths” during the pandemic were caused by bacterial pneumonia rather than the flu itself.
While historical estimates place global deaths from the 1918 pandemic around 50 million (with some estimates reaching 100 million), Fauci’s 2008 paper did not state an exact 90% figure for bacterial fatalities. The researchers stated broadly that the “vast majority” of deaths stemmed from secondary bacterial infections, noting the presence of bacteria in a specific subset of lung cultures examined. The specific “45 million” figure often cited online appears to be a back-of-the-envelope calculation derived from applying those specific autopsy percentages to global mortality estimates.
The Takeaway
Fauci and his fellow researchers published a 2008 study demonstrating that secondary bacterial pneumonia—facilitated by initial viral damage to the respiratory tract—was responsible for most deaths during the 1918 influenza pandemic. The study made no mention of face masks, and medical science has found no evidence that wearing masks causes bacterial pneumonia.